Messi would probably do the same thing he did before. He would rather be free agent first to see if he can get an agreement with Barcelona again. Then he would make his final decision about his future. If it doesn't happen then I think he would play for PSG one more year at least.
I don't think Messi will go to Arab or US leagues. He is a legend. He should leave football in a way that suits a legend. After the contract with PSG is finished, if he signed a 1 -year contract with Barcelona and leaves football, he will complete a great career. Messi does not need to go to Arab or US leagues. Messi will not be as helpless as Ronaldo. I think there will be big clubs that want to see him at least one more season in Europe.
I can't really tell what is next for Messi whether or not he will continue his career at PSG. Rumors have it that a move to Arab league is likely but I don't see a possibility of joining Ronaldo at Al Nassr. The rivalry between Ronaldo and Messi is a great story the way it already is. If you ask me I feel Messi will extend for a further year with PSG, when he decides to leave the club I think he will want to end his career in Barcelona. Messi is not the type of player who likes to explore different clubs and leagues as we have seen throughout his career, he’s played for only 2 clubs and I strongly believe he will be returning to Barcelona.
Messi is an extraordinary player and many clubs will try to bid for Messi to enter his club. If the contract with PSG ends, Messi hasn't decided where to go, whether to extend it or not. But there are several requests from Messi that PSG must do so that Messi can survive and extend his contract, such as a salary increase. It is known that salary currently received by Messi is $ 41 million per season and that is not enough for Messi, Messi asked the club to be able to increase his salary in renewing the contract with PSG and that would be PSG's main consideration, because even though Messi can appear competitively, Messi is already old. 35 and it is feared that its performance will decrease. Besides that, Messi also has PSG have new players who are talented and can keep up with him and can win his fifth Champions League hat. Messi's desire to be a champion is still very big and it must be supported by new talented players who can make a contribution at PSG in the Champions League.
After the 2022 world cup is over, Messi intends to retire from the Argentina team and will take more time off. But because the break was too long, PSG was worried that it would affect the team's condition, because other players would certainly be jealous of the others training hard while Messi was still resting.